Refill is another campaign that I have worked on since its inception and can be transferred to events.
We identified that people drank bottle water because it was a sign of health and it is easy and convenient to grab a bottle on the go.
Asking for free tap water brings up discomfort as it was previously not socially acceptable and it feels unacceptable asking for something free in a cafe when you are supposed to be buying something if the cafe doesn’t make it obvious it would offer it (Herd behaviour/conformity bias/authority bias).
So by creating a network of cafes and organisations that displayed stickers and were on an app, we were able to break down some of those fears (of rejection) and biases by signalling that it was acceptable socially and from a business perspective.
There are now thousands of refill points on the app including lots of mayor chains.
There is also lots of interesting data about when and why people carry a reusable bottle which re related to habits - to the Gym, to work but not at the weekend, to an event or on holiday (because of the perception it will be hard to refill). If you run an event you need to make it explicit in advance that people can refill and really remove the offer of bottled water to push people towards refilling (taking away the easy option).
Shambala is a plastic-bottle free event and I believe Glastonbury was planning to be this year. This means increasing the availability of tap water but the benefit is less waste and litter.